Using with NTP

The `chu` software can be used in combination with NTP to produce a stratum-1 time server.

This is done using the LOCAL reference clock module in ntpd. For example, if you are using ntpd version 4, the following configuration works nicely:

>       server 127.127.1.0 prefer
>       fudge 127.127.1.0 stratum 0 refid CHU
>       disable ntp

`chu` communicates with ntpd via the kernel's `adjtimex()` API. Note that `adjtimex()` is the Linux API, and may be called `ntp_adjtime()` on other systems.

The system clock is disciplined by `chu`, not by ntpd.

`chu` appropriatly maintains the status flags and error estimates so that `ntpd` can do the right thing.